Selective properties of laser resonators with diffraction grating operated in the autocollimation regime

Experimental and theoretical investigations were made of the frequency-selective loss functions of laser resonators with diffraction gratings operated in the autocollimation regime. Investigations were carried out in a wide range of parameters of resonators with circular aperture stops. The functions in question were calculated numerically by a variety of methods. The frequency detuning scales were generalized. A study was made of the influence of the position of an aperture stop, of the confocal parameter, and of the radial inhomogeneity of the active medium on the selectivity. An allowance for the lens effects in the active medium altered the nonselective losses but had little effect on the frequency-selective loss functions. The results obtained were found to be valid for resonators with beam expanders. A calculation was made of an "autograph" of radiation from a CO₂ laser with a diffraction grating. The results of the calculations agreed with the experimental data.